#9519: Add QuerySet.bulk_delete() that issues only a single SQL query
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Reporter: Tarken | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: database, queryset, | Needs documentation: 0
delete | Patch needs improvement: 0
Has patch: 0 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by akaariai):
API idea: How about qs.values().delete() doing a no-signals delete? We
could also implement the cascades by fetching the PK values to be deleted.
This should make .values().delete() faster and less memory hungry, yet
cascades are implemented.
To me this API seems correct - values() is doing "fetch the raw values
only, not objects" so values().delete() is doing "do the deletes by
fetching raw values only, not objects".
Currently .values().delete() doesn't work at all (except accidentally they
do for fast-path deletes...).
The disabling signals idea is dangerous if one can do global "signals
disabled" call. For example "with disable_signals(): do_something()" will
break `model.__init__` in do_something() for models having !ImageFields or
!GenericForeignKeys. To be safe the only way to disable the signals should
be by listing the signal target functions explicitly. In addition, the
disabling should be thread-safe and really fast (at least for the no-
signals-disabled case). `Model.__init__` is limited somewhat by
signal.send speed already. So, my initial feeling is to not do this.
I would love it if there was some way to tell the DB to set foreign key
constraints to ON DELETE CASCADE temporarily. But, there doesn't seem to
be any way to do this in SQL.
--
Ticket URL: <https://code.djangoproject.com/ticket/9519#comment:19>
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